Manual telephone system



Jan. 11,1927.

W. T. POWELL MANUAL TELEPHONE SYSTEM INVENTOR WINFRED T POWELL WE w W lvlmv ivivl Filed March 22. 1924 R; E, s

LIWMLI ATTORNEY Patented Jan. 11, 1927.

UNITED STATES P'f'ET OFFICE.

WINFRED 'l. POWELL, OF ROCHESTER, NEW' YORK, ASSIGNOR TO THE STROMBERG- CARLSON TELEPHONE TIIANUFAO'TURZNG COMPANY, 035 ROCHESTER, NEW YORK, A.

CORPORATION OF ITEVV YORK.

MANUAL TELEPHONE SYSTEM.

Application filed March 22, 1924. Serial No. 701,211.

This invention relates to manual telephone systems.

In former manual telephone systems, socalled feature cord circuits are provided which function to connect the operators tele phone set automatically to a' cord circuit when it is taken for use and for disconnecting this telephone set from this cord circuit, when it no longer needs the attention of the operator. These circuits also control means for automatically signaling the desired sta tion on a party line, when a ringing key has been momentarily depressed to select ringing current of the proper frequency. Other features of, these circuits include the extinguishing of all supervisory signals of a cord circuit when it no longer needs the attention of the operator, and in addition certain means function to count automatically, the number of calls answered by an operator. In many of the arrangements now in use, it is necessary to provide a strip of keys for each operators cord circuit, but in one arrangement now in use a single strip of ringin keys common to all of the cord circuits of an operators position, control the selection of the proper current to signal awanted station.

These so-called feature cord circuits require a large number of relays and in accorddance with one feature of the present invention it is proposed to replace a number of the relays of such a cord circuit by a progre sively movable switch.

Another feature of the present invention relates to the provision of a progressively movable switch to control certain of the functions of a manual cord circuit, in which but one common strip of keys is provided for controlling the connection of a desired one of several frequencies of signaling currentto all the cord circuits of an operators position.

A further feature of the invention resides in the provision of means whereby in a manual telephone system, when two stations on a party line are to be signaled, signaling current of the proper frequency to signal these stations is automatically connected to the party line.

Other features of the invention will ap pear from the detailed description and the appended claims.

The drawing diagramma'tically represents a portion of a telephone system including the present invention. At the upper left hand corner of the drawing there is represented the substation of a poly-station telephone line of the well known character terminating at the central office in multiple acks. At the upper right hand corner of the drawing there is represented a substation of a multi-party telephone line likewise terminating in the central ofice in multiple jacks. Above the dotted lines and in the center of the drawing there is shown a single manual cord circuit, of which each operator is provided with a plurality. Between the dotted lines there is indicateda second and a third cord circuit while below the lowermost dotted line there is shown the equipment common to an operators position, which includes a single set of frequency selecting ringing keys and relays, as well as an interrupter machine shown at the lower right of the drawing for applying ringing current from the generators indicated in the lower left hand corner of the drawing. 7

in the drawing there are indicated the elements of a sequence switch, which may be of substantially the same character as the switch shown in .the patent to Clement #1,107,l53, patented August 11, 1914, although other types of sequence switches may be employed.

The code machine associated with the ringing generators and indicated in thelower right hand corner of the drawing may be of any well known structure in which the various contacts are closed in the same relation as indicated in the diagram. The code machine may consist of a rotating shaft on which there are mounted segments of insulating material to actuate the several sets of springs.

lVith this brief statement of the apparatus used, it is believed thatthe invention will best be understood by describing the method of establishing a telephone connection from the substation such as that indicated at A to a wanted substation such as that indicated at B. lV hen the subscriber at A removes his receiver from its switch-hook, the line relay 1 is energized over the two sides of the calling line in series in the well known manner and thereby lights one or more line lamps, such as 2, to signal thervarious operators that substation A has originated a call. The operator at whose position the cord circuit or": this disclosure is located, inserts the answering plug 1 01 this cord circuit into amultiple jack of the calling line. This coinpletes an operating circuit through the wit handhigh resistance winding or relay 6, through the sleeve contacts of "he plug and jack 8 in series with the winding 01" the cutoff relay 5 to ground. The cut-oil relay 5 and the operators barring relay 6 are both energized in this circuit. The cut-oft relay 5 disconnects the line relay 1 :lro""i the calling line,wiiclrrclay in turn or. .nguishes the line lamp 2. The relay on energiization closes a locking circuit for itself through its right hand low resistance winding, its right hand front contact and armature and thence over the remainder of the circuit previously described as extending to ground through the cut oil relay 5. t will be noted that the operators barring relay (3 is energized through its high resistance winding and 1s held operated through its low resistance winding, thereby preventing the energizing of a relay. such as 6, at a second opcrators position, in case that a second operator connected an answering plug (it one of her cord circuits to a multiple jack of the calling line. Also when the operator connects the plug t to the jack 3, the answering supervisory relay 7 .is energized over the answering end of the cord circuit and over the two-sides in series of the calling telephone line. The energization of the relay 7 prevents the light; ing or the supervisory lamp 8 at this time. With the relays 6 and 7 operatedthe motor magnet 9 of the sequence switch is energized in a circuit completed. from groundedbattery, winding of this magnet, its armature and back contact, sequence switch contactrlO closed in position 1, left hand front contact and armature of relay 7, outer lctt hand front contact and armature of relay 6, Wll1(tingot the relay 11 to ground. The motor magnet 9 when thus actuated interrupts its cireuitand moves the brushes of the sequence switch to close contacts in position 2. If at this time no other sequence switch is standing in position 5 or 6, the common guard relay12'will be in its normal position, so that the motor magnet 9 is actuated in a circuit now extending from grounded battery, its winding, armature and back contact, sequence switch contact 13 closed in position 2, back contact and arn'iature of relay 12 to ground. Under the control of this last mentioned circuit, the motor magnet advances the sequence switch into position 3.

If, however, some other sequence switch associated with another cord circuit of this operators position is standing in position 5 or 6, the sequence switch under considera tion will not be moved out of position 2 because at that time relay 12 will be operated. Itwill be seen that a chain circuit is normally connected to ground through the armature and contact of relay 12, through all of the other sequence switches at this operators position, so that the operator may plug up as many answering cords in advance as she.

circuitto ground from the sequence switch contact 20, contact 21 and arn'iature of relay 15, conductor 22, back contact, armature and winding of motor magnet 9 to grounded battery. This circuit is ell'ective to advance the sequence switch from position 3 position a and into position 5. The relay is the-"eupon. actuated from ground, winding of relay 23, sequence switchcontac 2d and the r it hand winding of the calling supervisory relay 25 togrounded battery. The relays 23 and 25 are energized and the relay 23 connects the operators telephone set (not shown) over the conductors to the answering end of the cord circuit, so that the operator is now telephonically connected to the callin subscriber and may request the number or the wanted substation such as B. The operation of relay 25 is ineli'ective at this time.

It will be seen from the foregoing description that only one sequence switch of the cords located at this operators position can be advanced intoposition 5, so that the operators telephone setis connected to one cord circuit only at atime, The operation of the relay 23 extends a circuit from ground through the winding of the slow leasing relay 12, left hand armature and trout contact of relay 23, continuity spring and armature of relay 7, and thence to grounded battery through the lamp 8. The

energization of relay l2 completes a circuit A for operating the meta 2? and since the relay 12 1s ener zed only once for each call answered, this insures an accurate operatioi'r ot' the meter 2?. Provision is also made so that this meter may be in readiness to record an overlap call, that is, one which is started before the first connection is completed. l -then the sequence switch of the first connection leaves position 6, the relay 12 releases and moves the se uence switch o.=" the second cord circuit out of position 2 and since this last named sequence switch must be advanced to position5 before relay 12 is operated again, sufficient time is allowed tor the meter to release.

. l thi ouga lliil During the time that the operators telephone set is connected to the answering end of the cord circuit of a connection the guard relay 12 is held operated in a circuit completed through the left hand armature and front contact of relay 23 to grounded battery, either through the continuity spring and armature of relay 7 or through the continuity spring and back contact of this relay and resistance 28. The guard relay holds the meter in its operated position, which insures that no false registration occurs, even though the calling subscriber operates his switchhook and thereby causes the armatures of the super *isory relay 7 to vibrate. The operation of the relay 23 it will be remembered closes a circuit through the supervisory lamp 8 in series with the guard relay 12, so that this lamp is dimly lighted to indicate to the operator to which cord circuit her telephone set is connected.

After receiving the number of the wanted line the operator proceeds to test this line, by touching the tip of the calling plug 32 to the sleeve of the multiple jack of the wanted line. If the wanted line is busy this operation causes a distinctive click in the operators receiver, to indicate that the want. ed line is busy. If, however, no click is heard it is the signal to the operator that the wanted line is idle. This testing opera tion is effected in the Well known manner and need not be described further.

It should be pointed out that the sequence switch contact is closed in position 1, so that the tip contact of thecalling plug is connected to the common busy test key 31 and since all cords not in use are in position 1, the tip contacts are all normally connected to this key, so that the operator can test any line, even though the answering end of the cord circuit is not connected to a telephone line.

It is assumed that the wanted line when tested in the manner just referred to, is found idle so that the operator inserts the calling plug 32 into the multiple jack 33 of the called line, This closes a circuit from battery through the right hand winding of the relay 15, the sleeve contacts of the plug 32 and of the jack 33 and thence to ground through the cut-oil relay (not shown) of the called telephone line. It will be remembered that at this time the left hand winding of relay 15 is energized so that this relay which is differential in operation now retracts its armatures. This is effective to eX- tend a circuit from ground at sequence switch contacts 34., contact 35 and armature of relay 15, conductor 22, back contact, armature and winding of the motor magnet to grounded battery. Under the control of this circuit the motor magnet advances the sequence switch into position 6, where ringing current of the proper frequency to signal the Wanted substation, is selected. In this position the operators telephone is maintained in connection with the cord circuit by means of the relay 23, which allows the operator to be connected to this cord cir cuit, after the calling plug 32 is inserted in the multiple jack of the called line and until a ringing key is depressed. In posit-ion 6, also the calling supervisory lamp 37 is lighted in a circuit closed at sequence switch contact 360, in order to give a ringing indicaion. In this position, likewise, the relay 38 is actuated from grounded battery, its right hand winding, conductor 39, outermost back contact and armature of relay 15, equence switch-contact 36 to ground. The relay 38 when operated at its right hand armature and front contact applies ground to conductor 40, whereby the master ringing keys are effective to select the proper ringing current. The control of the conductor 40 at the relay 38 prevents the operation of any of the ringing keys when a sequence switch of a cord circuit it not in ringing position, from being effective.

Let it be assumed that the bell at the wanted substation responds only to cycle ringing current. The operator thereupon depresses ringing key 41 to actuate and lock the relay 4:2 in series with the relay 19, which is also actuated, thereby. Relay 19 opens the energizing circuit through. the left hand winding of relay 15, which allows this dif icrential relay to attract its armatures by reason of the circuit which now extends through its right hand winding. lVith the armatures of relay 15 attracted, it completes a circuit from ground, sequence switch contacts 36 closed in position 6, outermost armature and front contact of relay 15, con ductor 22, back contact, armature and wind ing of motor magnet 9 to grounded battery. Under the control of this circuit, the motor magnet advances the sequence switch to position 7. As the result of this switch leaving position 6, the relay 23 deenergizes to disconnect the operators telephone set from the cord circuit under consideration and at sequence switch contact 360 opens the lightcircuit for lamp 37. The original energizing circuit of relay 38 is also opened bythe operation of the sequence switch, but this relay is now maintained locked from grounded battery through its left hand winding, front contact and armature, back contact and armature of relay 16, sequence switch contacts to ground. At this time also, the motor magnet 9 has its actuat ng circuit closed from grounded battery, winding, armature and back contact of magnet 9, conductor 22, contact 21 and armature of relay 15, sequence switch contact 20 to ground.

It will be noted that the sequence'switch con-' tact 20 is closed in positions 7 to 1?, so that the last described circuit, unless otherwise control-led, is efiectiye to advance the i sequence switch through positions 7 to 17. However, when relay 42, corresponding to the 50 cycle currenhis selected, the sequence switch'isstopped inposition l2. lVhenthe sequence switch reaches this last named positionya circuitis closed from grounded battery, resistance at, upper armature and front con act of relay 19, inner, upper armature-and trout contact of relay L2, inner, upper arn'iature and back contacts of relays 45 and 4-6, ctmductorda', sequence switch con tact 48, back contact and continuity spring; of relay it}, left hand winding 01" relay 15, outer. ouch contact and armature of relay 1 ito ground. Since-both windings of relays are energized. at this time, it retracts its arniatures and stops the sequence switch in position Fifty cycle ringingcurrent is now applied-to the called line from the generator shown in the lower left hand cor nernotthe diagram, conductor 50, contact 51 ot-the interrupter whencain 52 is rotated through ninety degrees, conductor sequence switch contact 5 L closed in position 12, left hand winding of the trip relay 55, left handback contact and armature of relay 15 through the ring contacts of the plug 32 and the jack 83, over the lower side of the called line, through the ringer at the called station, which it is assumed responds to 50 cycle ringing current, over the upper side of the called line and through tne tip contacts of the jack 33 and the plug sequence switch contacts 56 to around. Ringing current is intermittently transmitted over this circuit under the control of the interrupter until the called subscriber answers at which time the trip relay attracts its armatures and edits innermost armature and trout contact closes a locking circuit for itselt' through its right hand winding to ground through the sequence switch contact 20. At the middle armature and contact 58 of relay the left hand winding of relay 15 is short-circuited thereby permitting this differential relay to attract its arma res. This operation closes the operating circuit for motor magnet 9, over the conductor 22, arnature and contact 2i oi relay 15, sequence switch contacts closed in positions 7 to 17. Under the control of this circuit, the motor nu, advances the sequence switch to position 18. This is the talking position and it will. be noted that the of qucnce switch contacts 59 and 60 are closd in this position to complete the conversa tional circuit. When relay 15 opera i opens the original cncrfzin circuit lay 16. but it closes a sail for, which is completed at. the middle arin'ature and contact 57 of relay to ground, so that the relay 16 is held operated until the sequence switch r aches position 18.

Talking l a tery supplied to the calling i die circuit theresubscriber:- through the. two i windings in series of the answer-111g supervisory relay 7 while talking battery is supplied to 1 the callediparty throi-ighboth windings 1n serles of the supervisoryrelay CODVGL'Sfl/UOIL may now take place.

[it the close of the conversation, when the subscriber at A replaces his receiver omitsswitchhoolr, the answering supervisory relay 7 deenerg'izes and thereby closes a OllCtllt from grounded battery through the answer my; supervisory lamp 8, back Contact and at mature of relay 7, outer, left hand, front;

contact and armature ot-relay 6, winding of relay 11 to ground. The lamp 8 is lighted in this circuit which is a signal to thecoperator that the connection is-terminated, whereupon she witl'idraws the answering plug and-the calling plug 32. from the J cks with which It the called ringing, positions 8 to 17 inclusive, these lamps are not lighted; an arrangement known as the dark keyboardfeature.

It the callingsubscriber abandons the call while the operators head set is connected to the cord circuit shown, that is, while.

the sequence switch is in posit-ions 5 or 6, relay 14s isnot operated. But it the sub scriber abandons the call while the sequence switch is StZIIIGllD 'lH positions- 7 to 17 inclusive, a circuit is closed from groundat the inner lett handarinature and front con-- tact of relay 6, sequence switch contact 62, outermost back contact and armature of relay '1, WllKllDgO'f relay l lato grounded battery. Relay 14 is thus actuated and closes a locking circuit for itselt through its left hand armature and front contact which is independentof the control'ot the relay 7.

Sequence switch contact (33'is closedin position 7 so that the relay it can be operated as soon as the sequence switch leaves the listening position, in order that there canbe'no possibility oi the sequence switclrstopping;

in the first ringing position such as 8. it the calling"partyabandons the call while the sequence switch is: in the ringing position, the Operation of relay l t at its outer right hand armature andiloaek contact opens the energizing; circuit for the left hand winding ot relay 15, which permits. this last named relay to operate by reason of the energizing circuit completed through its right hand winding. An operating circuit for the motor magnet 9 of the sequence switch is now closed over conductor armature and front contact 81, sequence switch contacts closed in posi ions *4 to 17 inclusive. Under the control of this circuit the sequence switch advances into position 18, where the supervisory lamps are lighted to give a disconnect signal to the operator.

If the calling subscriber terminates the call while the sequence switch is in position 18 and while the called party is connected to the cord circuit relay let is not operated, but if the called subscriber has replaced his receiver on its switchhook, a circuit is closed from ground at the inner armature and front contact of relay 6, sequence switch contact 6 1 closed in position 18, back contact and armature of relay 25, outermost back contact and armature of relay 7, winding of relay 1 1 to grounded battery. Relay 1 thus operated and closes a locking circuit for itself in the manner already desc ibed,

If the calling subscriber makes a recall by temporarily operating his switchhook to open his line circuit and then maintaining this circuit closed, the lamp 8 is intermittently lighted in a circuit closed from grounded battery, lamp 8, through the middle front contact and armature of relay 7,

inner armature and front contact of relay 14 to ground over conductor 65, through an interrupter device (not shown).

Let it be assumed that the called substation is located on the same telephone line as the station that originated the call. T his kind of a call, as is well known, is referred to as a revertive call. Under such a con dition when the calling subscriber initiates a call by removing his receiver from its switchhook, the previously described operations take place, which are effective to advance the sequence switch into position 5, wherein the operators telephone set is con nected to the calling line. The operator then inquires the number of the wanted party and on discovering that the call is revertive, removes the answering plug from the jack of the calling line which is effective to deenergize the relay 6 and thereby advance the sequence switch into position 6 through the contacts 67. In thisposition the left hand winding of relay 15 is energized in a circuit, which may be traced from ground, outer armature and back contact of relay 1 1, left hand winding of relay 15, continuity spring and back contact of relay 16, sequence switch contacts 17, over conductor 18, back contact and armature of relay 19, resistance 14, to grounded battery. l/V hen relay 15 is thus energized it closes a circuit for advancing the sequence switch into position 7, which circuit includes the motor magnet 9, conductor 22, outermost front contact and armature of relay 15, sequence switch contacts 36, closed in position 6, to ground. In this instance the sequence switch passes through position 6 mature and back contact of relay 6, inner-.

most front contact and armature of relay 15, winding of relay 16, sequence switch contact 68, right hand winding of relay to grounded battery. Relay 16 is thus energized, while the sequence switch is standing in any of its positions 7 to 17. Relay 16 when thus operated extends a circuit from grounded battery, resistance, its armature and continuity spring, left hand winding of relay 15, outer, back contact and armature of relay 14: to ground. Relay 15 remains energized to move the sequence switch to position 18 by a circuit completed through the motor magnet 9, conductor 22, armature and contact 21 of relay 15, sequence switch contacts 20 closed in positions 7 to 17 inolusive, to ground. Sequence switch contacts 68 are open in position 18, so that the operating circuit of relay 16 is opened and when this relay retracts its armatures, it breaks the energizing circuit of relay 15, which last named operation closes an operating circuit for the motor magnet 9, over conductor 22, armature and contact of relay 15, sequence switch contacts 84., closed in positions 18 to 20, to ground. Under the control of this circuit, the sequence switch advances into position 1. The operator now inserts the calling plug of her cord circuit into the jack from which she removed the answering plug of this cord circuit and this functions to energize the relay 15. The energizing circuit is closed from grounded battery through the right hand winding of relay 15, the sleeve contacts of the calling plug 32 and jack 3, winding of the cut-elf relay 5 to ground. With relay 15 in its attracted condition, a circuit is closed from ground, sequence switch contact 20 closed in position 1, contact 21 and armature of relay 15, conductor 22, winding of motor magnet 9 to groundedbattery. Under the control of this circuit the sequence switch advances to position 2, where an operating circuit for the motor magnet is extended through sequence switch contacts 67 closed in positions 2 to 5, inner back contact and armature of relay 6 to ground. This circuit advances the sequence switch to position 6. When the sequence switch enters position 3, a circu1t is completed from grounded battery, resistance 14, armature and back contact of relay 19, conductor 18, sequence switch contacts 17, back contact and continuity spring of relay 16, winding of relay 15, back contact and :arinature of-relay -14 to ground. This cir- :ouit energizes the left hand winding of relay .lr'nin opposition tothe right hand winding of this relay, so that it retracts its armatures. The operator now depresses two ringing keys such as 41 and 69 corresponding to the ringing frequencies, which will signal the wanted-station and the calling-station. The depressionof these last two keys energizes therelays42-and 46in serios'with the relay 1-9. These-relays when operated are locked .in'thiscondition 1 to ground over conductor -40. Relay 19 on operation opens thecircuit .througlrthe left hand winding of relay 1:"), :-so tliat thisrelay isenergized to complete i251, circuit over conductor iii-armature and contact 21 of relay'l5, sequence switch con tacts to ground, for movingthe l sequence :switch into theposition through which the 0 :proper ringing current is applied to signal .the" calling and called stations. In this instance the-sequence switch must be ad- -vanced to position 1 1. The stopping of the sequence switch in this position is effected by: reason of arcircuit traceable from ground through the armature and back contact of :relay'lt, left hand winding of relay 15, continuity spring and back contact of relay 16. sequence switch contacts 70 closed in position lhinnermost front contact and arn'iaturc 0t "relay- L6, back contact and armature of relay 45,- inner frontcontactend armature of relay l2, frontcontact and armature of relaylf), resistance 3A., to grounded battery. This cir ouit energizes the left hand winding of rel :rv 1l5'in opposition to its right hand winding, thereby-causing thisrelay tore-tract its armatures to open the: advancing circuit of the motor magnet of the sequence switch. Relay Miis thereupon actuated ttrom. grounded hattery, right hand winding of relay quence: switch contact68,winding o't relay 16,:innerm0st armature and back contact of relay '15, "sequence switch contact '20 to ground.

Ringing current isnow applied from the and 66 cycle generators and alternately over conductors 50 and? lVhen'the interrupter is in such a-position'that its cont-acts 71-are closed the :50 cycle source of ringing current is 'appli ed over conductor T6,-'sequenee switch contacts 7'? closed in pos'ition=14,-lefthand-winding oi the trip relay 55, lefthandbach contactand armature of: relay15, through'the ring contacts of the plug SQ-andjaclr 3,.over the lower side of the! telephone. line, through i the ringer that responds to-50' cycle ringing 'current, over the upper side of this telephone line, through theftip contactscof the jack and plug. and thencezto ground through the sequence switch contacts 56. When the contacts 72 of the in terru-pteriareclosechthe contacts 71 of t. Is interrupter are open. The 66 cycle source oi. ringing current-is then applied from generator 73, over conductor 74:, interrupter con tacts 72 and 75 and thence over the circuit including conductor 76, as previously-clescril ed, through the ringer at the station that responds to 66 cycle ringing current W] h the rwjht hand winding of relay 25, in a circuit that is completed through contact 57 andzmiddle armature of relay The left hand winding of relay 15 is short-circuited at this time in a circuit closed tromgrounded battery, resistance, armature and continuity spring of relay 16, contact 58 and. armature of relay "55, to. ground. Relay 15 thereupon attracts its armatures and at itsileft hand armature and back contact interrupts the ringing circuit just described. At the contact Q1 and armature of relay15, the operating circuit for the motor magnet 9 is completed over conductor22, sequence switch contact 20 closed in positions? to 17 inclusive to ground. ot to advance the sequence switch int-oposition 18, which is the talking position. lVhen the called party answers, the superiisory relay :25 operates and prevents the supervisory lamp'iii' from being lighted. Also when the called party answers, the hell at the call ng partys station ceases ringing, whichis an indication that the called party has answered so that the calling party removes his receiver from its switchhook and conversation then t'ZLlIQS- place.

lVhen both parties to the connection hang up their receivers, the relay 25 dcenergizcs and lights the supervisory lamp 37. This is a signal to the operator that the connection should he tern'iinated and she thereupon re moves the plug 32 frointhe jack 3. This etlccts the dcenergization of the relay 15, which in turn closes a. circuit through sequence switch contacts'34, Contact and armature of relay 1.) and thence over conductor22 through the motor magnet 9, which operates to advance the sequence switch into its normal position.

In the event that the called party does not answer in the case of such a revertive call, the calling party removeshis receiver from its switchhooh which is effective to stop the ringing and results in the advance of: the sequence switch to position 18. lVhcn now the calling party hangs up his receiver the supervisory lamp-37 is lighted in the manner already described to signal theopcn ator for disconnection, whereupon the quence switch advances into its normal posi- This circuit is effective a:

llll} iii tion. In the case last assumed when the calling party removes his receiver trom its switchhook, he may intermittently light the supervisory lamp 37 by moving his switchhookup and down. This is a signal to the operator to remove the calling plug and insert the answering plug of a cord circuit into the jack of this calling line. Thereafter the operator may listen-in on the connection and complete it in the manner alreadydescribed.

\Vhat I claim is:

1. In a telephone system, a plurality of telephone lines, a plurality of link circuits, each tern'iinating at each end-in a manual switch, a plurality of sources of current for signaling said telephone lines ever said link circuits, a ringing key individual to each of said sources of current, said keys being common to said link circuits, and a progressively movable switch for variably connecting said sources of current to a link circuit under the control of said keys, a-supervisory signal associated with each link circuit, and means including the progressively movable switch of a link circuit for operating the associated supervisory signal in a. distinctive manner in.

response to the initiation of recall over said last mentioned link circuit.

2. In a telephone system, a plurality ot telephone lines, link circuits for interconnecting said telephone lines, each of said link circuits terminating at each end in a manual switch, a plurality of sources of ringing current for signaling said lines over said link circuits, a single key for each of said sources of ringing current, said keys being common to said link circuits, a progressively movable switch at each link circuit for connecting one of the various sources of ringing current to its link circuit in each of several of its stopping positions, means including said keys tor determining the stopping positions of said progressively movable switches. a calling supervisory signal for ea"h link circuit, and means including the progressively movable switch of a link circuit for operating the associated supervisory signal in the course of each call prior to the application of ringing current to said link circuit.

In a telephone system, a plurality of telephone lines. a plurality of link circuits for interconnecting said telephone lines, each link circuit terminating at each end in the contacts oi a manual switch, plurality of sources of current for signaling said lines, a key individual to each source of signaling current, said keys being common to said link circuits, a progressively movable switch in certain of its stopping positions connecting a source of current to a cord circuit, a relay having an operating circuit extending through contacts of a link circuit, other means including one of said ringing keys for controlling said relay in the various positions of said progressively movable switch, and means including said relay for stepping said progressively movable switch in any one of a plurality of positions for connecting a predetermined source oii' ringing current to a link circuit.

i. In a telephone system, a plurality of party lines, link circuits for interconnecting said lines, each link circuit terminating at each end in a manual switch, an operators telephone set common to said link circuits, a plurality of sources of ringing current of the proper character to selectively signal the stations on a party line, and means including a progressively movable switch individual to each link circuit for connecting said operators telephone set to one link circuitat a time and for selectively connecting a desired source of signaling current to said link circuit to selectively signal a party line.

5. In a telephone system, a plurality of telephone lines, each telephone line being provi led with a plu 'ality of substations, a plurality of link circuits for interconnecting said telephone lines, each link circuit terminating at each end inthe contacts of a manual switch, a plurality of sources of current for selectively signaling the substations on a party line, a key individual to each source of signaling current, a relay individual. to and arranged to be operated by each key, said keys and said relays being common to a plurality of said link circuits, a progressively movable switch for each link circuit functioning to connect a different source of signaling current to a link circuit in each ot several. of its stopping positions, a differential test relay for each link circuit controlling the stopping of its associated n'ogressively movable switch, a primary circuit for said test relay completed through contacts of its link circuit, and a second circuit for said test relay variably controlled by said first mentioned relays.

(i. In telephone system. a plurality of telephone lines, each telephone line being provided with a plurality oi substations, a plurality of link circuits for interconnecting said telephone lines, each link circuit terminating at each end in the contacts of a manual switch, a plurality of sources of current for selectively signaling the substations on a party line, a key individual to each source of signaling current, a relay individual to and arranged to be operated by each key, said keys and said relays, being common to plurality of said link circuits, a nrogressively movable switch for each link circuitfunctioning to connect a different source OI signaling current to a link circuit in each of several of its stopping positions, a test relay for each link circuit controlling the stopping of its associated progressively amovalale switch, a'primary circuitlor said test relayextending through a manual contact, :and a second circuit for said test relay variably controlled by'sai'd first mentioned rclavs.

'7. In a'telephone system, a calling telephone line and .a called telephone line, link circuits for interconnecting said telephone lines, each of said linkcircuits terminating at-ieach'end in a manual switch, a progressivcly movable switch individual to each link circuit, an operators telephone set co1n- 'mon to a plurality of link circuits, means includinga progressively movable switch of -ZI-Illl1k circuit taken for uselor connecting said operators telephone set to said last mentioned link circuit, means including a -a recall from said calling telephone line.

while said telephone lines are interconnected.

8. In a telephone system, a plurality ol telephone lines, each telephone line being provided with aplurality of substat ons, the substations'of a telephone line being pro vided'with signals responsive to signaling currents of dilierent characteristics, link circuits for interconnecting said telephone lines in pairs, and means under operators control when twosubstationsof a-telephone line are called over a link circuit for automatically and alternately connecting to the link cir cuit the sources of ringing currentotthc proper characteristic to signal said stations ot said last mentioned line.

9. In a telephone system, a plurality of telephone lines, each telephone line being provided with a plurality of substations, the substations of a party line-being provided with signals responsive to signaling currents of dillerontcharacteristics, link circuits'for interconnecting said telephonelines in pairs,

means under opcrators control when two stations of a telephone line are called over a link circuit'l or automatically and alternate ly connecting to the link circuit the sources of rine'in current of the arc )er characterc: t: l

iistlc to signal said stations on said last men- 'tioned telephone line, and means actuated on the response ot either of said stations for are called over a link circuit for autoi'natically and alternately connecting to the link circuit, the sources of ringing current of propercharacteristic to signal said substations of said last n'icntioned telephone line.

11. In a telephone system, a plurality of telephone lines, each telephone line being provided with a plurality of substations, the substations of a telephone line being provided with vsignals responsive to signaling currents of different characteristics, link circuits for interconnecting said telephone lines, means including a progressively movable switch under operators control when two substations on the same telephone line are called over a link circuit for automati cally and alternately connecting to the link circuit, the sources of ringing current of proper characteristic to signal said substations of said last mentioned telephone line, and means actuated on the response of either of said stations for disconnecting said sources oi signaling current from said last mentioned telephone line.

In Witness whereof, I hereunto subscribe my name this 21st day of March A. l). 1924.

lVINFRED T. POW ELL- 

